This application claims the priority of German Patent Application No. 101 06 989.8 filed Feb. 15, 2001, which is incorporated herein by reference.
The invention relates to a latch needle, particularly for knitting machines.
Some knitting machines require latch needles whose latches have not only a rear position and a closed position, but at least one further pivoting position, in which the latch is flexibly held and does not rest against the hook or the needle shank. The latch that is pivotably seated in the sawslot is in contact with a leaf spring disposed in the sawslot. U.S. Pat. No. 3,050,968, for example, describes a latch needle of this type. The latch needle disclosed here is provided with a sawslot whose floor has a curved outline and is provided with an opening that leads to the back of the needle. The curved leaf spring rests against one end of the pivotably-seated latch, which end is directly adjacent to the latch seat. The two ends of the leaf spring rest against the floor of the sawslot, and span the opening. In at least one embodiment, at least one end of the leaf spring is secured to the needle body with respect to the longitudinal direction of the leaf spring. One chamfered end of the leaf spring extends into a small bore or opening formed in the floors of the sawslot.
German Published Patent Application No. DE-OS 1410312 discloses a similar latch needle, in which a leaf spring is likewise disposed in the sawslot. Unlike the needle in accordance with the above-cited prior art, however, this needle is not completely straight. Its center segment, which is in contact with the latch, has a curved region that conforms to the latch end. This arrangement secures the leaf spring in its longitudinal position. The free ends of the latch spring merely lie against the floor of the sawslot. In a further embodiment of the latch needle that is known from this document, the ends of the leaf spring lie in stepped shoulders formed at the floor of the sawslot. These shoulders, which are open to the top, each have a support surface for the respective end of the leaf spring, against which the spring rests due to its own spring tension. The spring tension is present because the end of the latch shank bends the leaf spring downward in the direction of the needle back, and the ends of the leaf spring rest on the support surfaces of the stepped shoulders.
A common feature in the prior art is that the spring is held between the latch end and the bearing seats, which are formed either by the floor of the sawslot or by separate stepped shoulders formed therein. The prestressing under which the spring is seated in the sawslot determines how reliably the spring is held in the sawslot. The greater the selected prestressing, the greater the friction and the force between the latch and the leaf spring. This can make the latches sluggish, and adversely affect the functioning capability of the latch needle, which in turn negatively influences the uniformity of the stitch formation. In an extreme case, sluggish latches will tear the threads, which leads to a halt in production.
Furthermore, it cannot be ruled out that the leaf spring may fall or be pushed out of the sawslot, at least in atypical operating situations.
It is therefore the object of the invention to provide a latch needle having an improved functioning capability.
The above object is achieved according to the invention by a latch needle that has an oblong or elongated leaf spring that is disposed in the sawslot and is held by its ends at corresponding bearing seats. The bearing seats are disposed at the narrow sides or end faces of the sawslot, and have a respective support surface and at least one counterpart surface located essentially opposite the support surface. The end of the leaf spring is therefore held between the support surface and the counterpart surface, and cannot leave the bearing seat. The counterpart surface can be formed as a projection that is connected to the narrow side of the sawslot, or on one or more projections provided at the elongated sides or edge cheeks of the sawslot.
This embodiment of the bearing seat with a support surface and a counterpart surface permits two options for mounting the leaf spring.
First, the spring end of the leaf spring is held with a form fit, and with little play, in the bearing seat. The leaf spring can therefore execute both a certain axial movement, as well as a pivoting movement, at least in a sufficient range, unimpeded.
In another mounting option, the leaf spring is mounted under a prestress, so its ends are held in the bearing seat without axial play and under tension.
In both options, the ends of the leaf spring are clamped loosely (i.e., so as to pivot and be axially displaced within limits). Despite this, the leaf spring is reliably prevented from inadvertently falling out. The function of the latch needle is thus maintained. This prevents errors or impediments to function that could occur if the leaf spring were to be lost.
Despite being secured by both ends in the bearing seats, the spring maintains its spring characteristic. Impediments to the spring characteristic, as would occur if the ends of the leaf spring were welded to the bearing seats or otherwise fixed to be axially stationary, are precluded.
A further advantage of the latch needle according to the invention lies in the greater flexibility in designing the shape of the leaf spring and its spring characteristic. For example, the leaf spring can be formed such that it is not permanently in contact with the end of the latch. Consequently, the friction between the leaf spring and the latch can be reduced, which permits the production of needles having a particularly easy-running, spring-supported latch.
The needle in accordance with the invention is not only insensitive with respect to various operating conditions, but also with respect to unforeseen handling, such as being blown with compressed air, for example, to clean the knitting machine. The leaf springs are held securely due to the special embodiment of the bearing seat, so the compressed air only causes them to slide slightly, and cannot blow them out of the sawslot.
In an advantageous embodiment, the leaf spring is held at the bearing seats such that it is displaceable axially, that is, in its longitudinal direction, to a limited extent. This means that the spacing between the bearing seats is slightly larger than the axial length of the leaf spring in the mounted state, so the leaf spring has axial play. The axial position of the leaf spring is determined by, for example, a region of the leaf spring that is curved in a V-shape or other shape and is in contact with the bearing-side end of the latch. This can reduce the influence of production tolerances, in terms of the precise arrangement of the latch seat and the position of the leaf spring, on the function of the latch needle. In addition, the impediment or influencing of the spring characteristic will be prevented because the spring is not clamped to or in the bearing seal. In another embodiment, the ends of the leaf spring are held under tension at the bearing seats. Here, the leaf spring cannot be displaced in the axial, that is, longitudinal, direction. It is therefore possible to influence the prestressing of the leaf spring. Also in this embodiment, it is critical that the ends of the leaf spring not be permanently or rigidly fixed. They are tensed, but can move in the bearing seats.
The bearing seats are preferably formed such that the leaf spring is not fixedly clamped to the bearing seats. The leaf spring is seated to move. This contributes to the functioning reliability and quality of the latch needle. The bearing seats do not negatively influence the spring characteristic.
The counterpart surface and the support surface can form a pocket, into which the relevant end of the leaf spring projects. This represents a particularly reliable method of seating of the leaf spring.
The latch needle can be formed such that the leaf spring rests permanently against the latch in a region between its ends, and is therefore prestressed. As an alternative, however, a slight distance can be present between the latch and the leaf spring, so the latch only rests against the leaf spring when the latch is in the vicinity of its end positions.
Advantageous details of embodiments of the invention ensue from the drawing, the description or the dependent claims.
The drawings illustrate exemplary embodiments of the invention.